Exposure to ionizing radiation is considered to be dangerous for humans. The rays or particles can do damage to human tissue to an extent that is dose dependent: the more radiation, the more damage. One theory on the relationship between absorbed radiation dose and the probability of health effects is that it is approximately linear without threshold, which would mean that there is a possible risk of health effects with any dose, however small. While there may indeed be no absolutely safe dose, there are dosages that are considered acceptable for practical purposes and unlikely to produce health effects. The risk of exposure is also dependent to a certain degree on the length of time over which the exposure occurred. The body can tolerate small doses that add up over time better than the same exposure all at once.
All humans are exposed to some radiation simply by living on earth. This naturally occurring or so-called background radiation comes from the radioactive decay of naturally occurring radioactive elements in the earth's crust. In addition to this, other sources of radiation are part of the course of everyday life such as dental or medical X rays, microwave radiation, luminous watch dials, color televisions, cosmic radiation, smoke alarms, and exit signs. A variety of sources of exposure to extremely small doses which add up slowly over time since dosage of radiation is cumulative over a lifetime.
The most commonly known destructive application of radiation is atomic bombs and/or military applications of radiation. Another commonly known application is atomically/nuclear fueled power generation. The electromagnetic radiation released by an atomic bomb, covering more-or-less the entire electromagnetic spectrum, can penetrate deeply into human tissue to damage human cells. The threat posed by atomic bombs has arguably increased in recent years with the growth of terrorism and the very real possibility that a “dirty bomb” can be made by terrorists through use of readily available nuclear waste and commercial application materials. Another source of concern comes from nuclear power generation, which produces byproducts dangerous to the public and surrounding environment as well as providing an additional route for supply of radioactive materials to terrorist organizations. The destructive threat to humanity of such nuclear bombs has given rise to a need for cost-effective radiation protection, including the need for lightweight radiation protective garments. Ideally, such lightweight radiation protective garments would simultaneously provide protection against other types of hazards, such as fire, chemical, biological, projectile hazards and other forms of electromagnetic radiation. In this way, first responders, such as firemen, paramedics, policemen or the military (and aerospace) could use a single garment to provide them with protection against any type of hazard they might foreseeably confront. Broad-spectrum portable/mobile protection, such as, but not limited to, hybrid radiation-ballistics protection has, until now, not been feasible due to, but not limited to, weight and financial resource limitations as well as a lack in available technology. Such “universal” protective garments are also addressed in Applicants' application Ser. No. 10/620,954, filed Jul. 16, 2003, entitled “Multiple Hazard Protection Articles And Methods For Making Them”, the disclosure of which is incorporated herein by reference in its entirety for all purposes.
A number of constructive uses have also been developed for harnessing radiation. These constructive uses include, but are not limited to, medical x-rays diagnostics, nuclear power generation, and radiation based material and structural analysis found in fundamental and applied sciences and engineering. Presumably, many other constructive uses of radiation remain undiscovered.
When an exposure occurs over an extended period of time, it is referred to as “chronic exposure.” Chronic exposure to radiation may occur naturally and in the course of daily life. Persons working in the nuclear industry or utilizing a radiation source in the course of their work receive additional exposure. Standards have been set to protect such workers from dangerous dosages of radiation. However, these standards tend to change (lower) as more is learned about the effects of radiation on the human body. A principal exists in the field of radiation protection, which is referred to by the acronym “ALARA”, which stands for As Low As Reasonably Achievable. Under this principle all exposures are kept to standardized minimum. In addition, the industry is required to take measures to reduce exposure if they can do so at a reasonable cost. In order to monitor occupational exposures, the worker wears a film badge or “dosimeter” to measure the amount of radiation to which they are exposed. Records are kept of the readings so that cumulative dose tabulation can be kept. Recent recommendations have resulted in a lowering of the maximum acceptable exposure. As indicated by the Uranium Institute, “Dose limits are considered to be the maximum acceptable exposure for an individual but they do not represent an acceptable level of exposure for a large number of individuals, or a level of exposure to which an individual can be repeatedly exposed.”
There are numerous international, federal and private organizations that disagree on how much exposure is “unhealthy”. Some feel that any dose of ionizing radiation, no matter how small, has the potential to do cellular damage. Others believe that there is not enough evidence to support such claims. One common agreement, however, is that there is no one standard physiological reaction to specific levels of radiation. Some people are able to tolerate certain types of radiation better than others. Persons exposed to the same sources of “acute” (short-term) radiation can end up later in life with very different physiological results. Ultimately, it is important for those concerned to investigate all current avenues of research and keep radiation exposure to an absolute minimum. DeMeo and others have described the incorporation of radiaopaque materials and non-woven fibers (see; U.S. Pat. No. 7,476,889; incorporated hereby by reference in its entirety). Furthermore, advanced techniques in extrusion and compounding allowed the higher loading of these radiopaque compounds to create a flexible garment. It is understood that the more dense and thinner the material, the more efficient it is in attenuating radiation. In order to increase the load of radiopaque materials in filaments, films, and fabrics, DeMeo had incorporated nano-metals as described in U.S. Pat. No. 7,476,889. Although this allowed for better radiation attenuation, the cost of the materials and the limited supply limits their applications.
Typical nano-metal manufacturing involves techniques as described in the art, e.g., in U.S. Patent Appl. No. 2008/0226535, U.S. Pat. No. 7,410,650 and U.S. Pat. No. 7,678,359. In all of these processes, the nano-metal is made from the anatomic level and built upward to create a nano-metal. Further, the processes described in these references are not scalable in that yield is quite low and thus, economically, not practicable. The instant application describes the first process to manufacture nano-metals from the macro level downward. As described further herein, in some embodiments, Applicants' methods comprise providing, e.g., a bulk compound, such as tungsten (W) and then convert it directly to mono dispersed chemical product (nano metal). In doing so, large amounts of metal nanoparticles can be made in a commercial scale and at a fraction of the cost.
Thus, there is a need in the art for compositions useful for radiation protection. The compositions and methods provided herein meet these and other needs in the art.
In addition human and assorted biological protection needs from various forms of radiation, there are multiple other areas where radiation attenuation is desirable. Various electronic systems, be it land, air, sea, and space based, are known to be particularly sensitive to radiation that can cause errors in functionality as well as partial or total system failure. Componentry critical to research, medical treatment, as well as defense systems require controlled isolation from various radiation sources and thus provide an additional demand for materials advancement.